Production of catalysts



- Th, V, Cr, Mo, W, U, Mn, Fe,

Patented Mar. 23, 1948 PRODUCTION OF CATALYSTS Raymond C. Archibald, Berkeley, and Bernard 8.

Greensi'eider and Frank T. Eggertsen,

CaliL, assignors to Sh pany, San Francisco,

Delaware ell Development Com Calii'., a corporation oi! N Drawing. Application February 20, 1946,

' Serial N0. 649,122

7 Claims. (01. 252-259) i This invention relates to the production of mineral inorganic oxide gel catalysts possessing a large available surface per unit weight.

For manycatalytic reactions and conversions catalysts having extremely large available surfaces per unit weight are desired. Such catalysts are prepared either by preparing the catalyst in the form of a, xerogel or aerogel or by applying the catalytic agent or promoter to a support or base having a gel structure. These gel catalysts when properly prepared have a micro- Dorous structure which afiords an available surface of at'least 100 mi /gm. and often in the neighborhood of 200-600 mfi/gm. Various oxides such as those of Be, Mg, Zn, Al, Si, Zr, Sn, Co and Ni as well as numerous combinationsjoi those oxides with each other and with other oxides have been prepared in a microporous gel state for use in catalysis. i

The most common method of preparing such catalysts is to produce the hydrous oxide in substantially an amorphous or sol state by any one of the variety of well known methods applicable with the particular composition andjthen to carefully dehydrate the product. Such a. product is called a xerogel.

In few cases these products are prepared as aerogels. in the pores of the material is removed while holding the material under pressure and at a temperature above the critical temperature of the liquid. In some cases this is considered an advantage since it prevents Orflecreases rupture of the cell walls by capillary forces and results in a somewhat larger available surface. most cases, however, no appreciable improvement is obtained by this more expensive and troublesome method and it is very seldom used. In still other cases the aerogel is quite inferior to the xerogel.

According to the process of the present inven tion inorganic oxide gels are prepared in a state more suitable for catalysis by a, practical and advantageous treatment which involves displacing the water with alcohol or similar non-aqueous liquid, heating under pressure, and suddenly releasing the pressure.

The process is particularly suited'and advan In preparing the aerogel the liquid butanols, the lower boiling aliphatic placed by the alcohol or high that the'liquid evaporated without furtherheating of the ex-' ploded gel. However, the temperature should not be as high as the critical temperature of the sistlng substantially of the oxides oi Si, Al, Zr, and Mg, alone and in various combinations. Thus, it is particularly suited for the-production oi the various so-called synthetic cracking catalysts comprising substantial amounts of two or more of these oxides. The process is however also applicable for the production of other metal oxide-gel catalysts such as mentioned above. In making these catalysts the hydrous gels may be prepared by any of the numerous known methods.

The hydrous gels are predominantly water and in most cases the water content is in the order of -95%. Prior to drying the gel most of this water is replaced by an alcohol or other suitable non-aqueous liquid. It is not essential that all of the water be removed. In fact, there is a. small amount of relatively firmly bound water which is exceedingly difilcult to remove. ever, the displacement ispreferably reasonably complete. The displacement of the water may be most effectively carried out by continuously washing the gel with a slow stream of the dis- HOW- "placing liquid, for instance by continuously slurrying and filtering or by passing the displacing liquid in a slow stream through a, tower or tray filled with lumps of the hydrous gel. Suitable liquids to displace the water are organic liquids which are at least partially miscible with water and have normal boiling points below about 200 C. Methanol, ethanol, the propanols, the ketones and the lower boiling aliphatic amines, for example, are suitable. Isopropyl alcohol is a preferred agent because of its superior vaporizatlon characterlstics.

When the water has been substantially disother agent, the gel is heated under pressure and then expioded" by sudden release of the pressure. I

The temperature prior to release of the pressure is appreciably above the normal boiling point of the liquid and is preferably sufilciently is substantially completely liquid present. If the temperature is above the critical temperature of the liquid the 'onlyexpansion effect possible is the expansion of the small amount of gas in thepores due to the dec eeses crease of the pressure, whereas at temperatfires tured gel catalyst having an available surface oi below the critical temperature the small amount of liquid in the pores is expanded to a relatively large volumeoi gas giving the desired exploding eflect.-

The pressure prio'r the vapor pressureot the liquid component at the prevailing temperature and may be increased beyond this. if desired, to increase the explosive eilect by pumping in a gas such as.- air, nitrogen, carbon dioxide or the like. The pressure should be at least 100 p. s. i. and is preferably considerably higher. v, R

The exploding of the gel may beefl ected batchwise, for instance by suddenly releasing the pressure on an autoclaved batch of the gel, or.it may be carried out continuously, for instance by iniecting under pressure the gel suspended in a stream of the liquid into a low pressure chamber at such a rate as to obtain an equivalent exploding efiect. The material used to displace the water-may be recovered and reused.

After the gel has been exploded it may be further calcined to increase the strength, and/or impregnated with one or more promoting agents desired in. the catalyst. v v

The catalysts prepared as described are somewhat diflerent from the hitherto-used xerogels and aerogels due to the exploding treatment.

' The exploding treatment causes a general expansion of the pores. Gels having large pores are found to be much superior to the usual finepored xerogels and aerogels for certain pu poses. This is particularly the case with the synthetic siliceous gel catalysts used in catalytic cracking. 5 Also, it is found that in some catalytic reac-- tions the rate'oi diffusion of the reactant and reaction products through the catalyst particle is a controlling iactor. The exploding treatment also causes rupture of certain of the cell walls and thus leads to a more open structure which favors fast diflusion. The exploding treatment in many cases also affords a product or somewhat larger available surface per unit weight. How-- ever, the increase in the available surface is generally only a fraction of the totaLavallable surface and is not of great importance.

The gels can easily be exploded without-first displacing the water with alcohol or one' of the other liquids mentioned. However, it should be particularly pointed out that this leads to exploded gels which are much inferior to the hitherto-used xerogels and aerogels. This is believed to be due to contact of the gel with steam. Thus,

in general, it is advisable to avoid all unnecessary heating of the gel in. the presence of substantial amounts of steam orwater.

Example A silica-alumina hydrogel containing about 8.85% silica, 1.25% alumina and 90% water and prepared by one of the accepted methods was used to prepare a catalyst. The silica-alumina hydrogel was the same as that used in preparing a commercial cracking catalyst and when dried at atmospheric pressure gave a flne-pored xerogel catalyst having an available surface of about 500 mF/g. This hydrous gel was treated with isopropyl alcohol to produce the corresponding alcogel. The alcogel was then placed in an autoclave provided with a bursting disc assembly adjusted to explode the material at 375 p. s.i. and at a temperature of 197 0. Upon heating the autoclave the gel was exploded at these conditions. The exploded product was an open-struc-,

. 5 ing the water with alcohol. to exploding is at least 51'! mils.

ploding the same gel but without first displac- The conditions of the explosions and the available surface areas totbilahe exploded gels are given in the iollowins a e: H

. assure, Temp., Surface Gal p. s. i. "O. mfilgmf The invention claimed is: 1. Process for the production or gel type catalysts.which comprises displacing water in a hydrous inorganic oxide gel with a non-aqueous organic liquid at least partially miscible with water and having a boiling point below about 200 C., heating the gel with said liquid under a pressure or at least 100 p. s. i. to a temperature between the normal boiling point and the critical temperature of said liquid and then exploding the gel by sudden release of the pressure. I

2. Process for the production of siliceous gel type catalysts which comprises displacing water in a hydrous siliceous oxide gel with a non-aqueous organic liquid at least partially miscible with water and having a boiling point below about 200 C., heating the gel with said liquid under apressure of at least 100 p. s. i. to a temperaturebetween the normal boiling point and the critical temperature of said liquid and then explod ing the gel by sudden release of the pressure.

3. Process for the production of silica-alu- 4 mina gel catalysts which comprises displacing water. in a silica-alumina hydrogel with a nonaqueous organic-liquid at least partially miscible with water and having a boiling point below about 200' C., heating the gel with said liquid under a pressure of at least 100 p. s. i. to a tem- .,peraturc between the normal boiling point and the critical temperature of said liquid and then I *exploding the gel by sudden release of the pressure.

4. Process for the production of gel type catalysts which comprises displacing water in a hydrous metal oxide gel with an alcohol having a boiling point below about 200 C., heating the gel with said alcohol under a pressure of at least 100 p. s. i. at a temperature between the normal boiling point and the critical temperature oi said alcohol and then exploding the gel by sudden release of the pressure.

5. Process for the production 01 gel type catalysts which comprises displacing water in a hydrous metal oxide gel with isopropylalcohol, heating the gel with isopropyl alcohol under a pressure of at least 100 p. s. i. to atemperature between the normalboiling'poirit and the criti- 5 cal temperature of isopropyl alcohol and then exploding the gel pressure.

6. Process for the production of gel type catalysts which comprises displacing water in a hy 7 drous metal oxide gel with isopropyl alcohol,

heating the gel with the isopropyl alcohol under a pressure oi! about 400p. s. i. to a temperature of about 200 C. and then exploding the gel by sudden release of the pressure.

'7. Process for the production of'silica-alumina by sudden release or the gel catalysts which comprises displacing water in a silica-alumina hydrogel with isopropyl alcohol, heating the gel with the is'opropyl alcohol under a pressure of about 400 p. s. i. to a temperature of about 200 C. and then exploding the gel by sudden release of the pressure.

RAYMOND C. ARCHIBALD. BERNARD S. GREENSFELDER. FRANK T. EGGERTSEN.

REFERENCES CITED The following references are of record in the Number UNITED STATES PATENTS Name Date Connolly --NoV. 14, 1933 Kistler Sept. 21, 1987 Morgan et al. June 8, 1989 Kellogg Nov. 28. 1989 Patterson Feb. 19, 1948 

